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Category Archive for ‘Blog’

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Crumb Handling System

When a food manufacturing firm in Sydney had a requirement to feed bulk crumbs mixed with oils out of pallecons and into a process line, they knew they had a challenge on their hands.

The product compacts under its own weight causing it to bridge and rat hole, making it hard to deliver into conveyors.

Fresco Systems was able to prove through a series of product trials they had ability to work with the product. Fresco then designed and quoted a system that would allow the client to reduce the physical handling of the product while maintaining a continuous throughput, thus both reducing costs and improving productivity. The system provided is completely unmanned except for the loading and unloading of the bulk materials.

Fresco Systems design philosophy makes it a natural choice for this type of application – where ergonomics, safety and productivity go hand in hand. For this application it was imperative that all contact materials were manufactured to the highest standard from 316 S/S and incorporating full safety guarding and interlocks to a category 3 level.

The custom designed solution incorporates a hydraulic bin tipper, with a graduated tipping angle to allow an even flow of product through a mesh into the charging hopper. The hopper was specifically designed with an agitator and fluidisers to negate any chance of bridging or flow issues. This then feeds a charging adaptor for the flexible conveyor, which is tuned via a VSD to match the downstream flow requirements.

This complete system had to fit within tight space requirements meeting site specific protocols around operator access to controls and forklift loading of bulk materials.

Fresco systems is the obvious choice when the requirements are for anything that requires thinking outside of the square, with a team of specialist engineers they are able to customise the solutions to cost effectively meet or exceed the clients expectations.

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Dust Free Bulk Bag Unloading

The use of flexible intermediate bulk containers (FIBC’s) or bulk bags as they are more commonly referred to have many benefits for the transportation and storage of raw materials such as powders and granules.

Fresco Systems have designed a solution for the safe discharging of bulk bags in a clean, dust free environment. This improves production efficiency and eliminates housekeeping issues caused through lesser processes.

Dust Free Bulk Bags are loaded in to the bulk bag unloader by forklift or electrical hoist and trolley. The bags are supported on the massage plates which protect the operator and through agitation will dislodge materials which may have compacted during storage or transport. The spout of the bulk bag is clamped in Fresco’s unique single handed spout clamp providing a dust tight seal that won’t leak or release during the discharge cycle.

As product discharges from the bulk bag into the process below displaced air vents to the integral or central dust collection system. This creates an air curtain at the spout of the bulk bag and a vacuum within the empty bulk bag collapsing the bulk bag so when remove from the bulk bag unloader it can be disposed of without bellowing dust and air into the environment as the operator folds the bag for disposal or recycling.

All Fresco systems bulk bag unloaders are independently load tested and certified as per AS/NZ 1418.

Fresco Systems designs, manufactures and install process system in-house providing a great deal of flexibility with adapting their standard designs to meet each customer’s specific requirements. Fresco Systems can change materials of construction, finishes, heights etc and adapt the discharge of the bulk bag unloader allowing materials from the bulk bag to be directly discharged in to packing machines, flexible or pneumatic conveyors, hoppers etc.

If you require a safe clean dust free environment for your bulk bag unloading contact us.

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Bulk Bags to Packaging Equipment

More and more of our customers are separating the blending and packaging process.

Where in the past they directly pack from under the blender, they now blend into bulk bags which separate the blending to the packaging process.

This has many advantages including independent scheduling on both operations.

Fresco Systems assist customers by fitting our bulk bag filling head under the existing blenders. Our single hand operated spout clamp and venting system enables quick and dust tight connection between the blender and the bulk bags. The bulk bags will then need to feed a form fill seal machine or any other packaging equipment. The packaging equipment usually provides a start/stop signal which is controlled by its weigh hopper.

Fresco Systems supplies various types and combinations of this system into the industry and recently we supplied an electric hoist type unloader coupled with a flexible conveyor to feed pre-blended flour products into a form fill seal machine. Due to the various type of pre-blend that needs to be fed, Fresco Systems selected the beveled spiral flexible conveyor which is capable to handle difficult products which packs, smears and compacts. This selection combined with the incorporation of vibration and agitation in the charging hopper ensures that the product flows consistently. A hinged hopper cover was also supplied to allow loading of smaller batch products. The start/stop signal from the packaging equipment communicates with our supplied control system which triggers and activates all the required flow aids above including bag massagers and the flexible conveyor.

Our experience and detailed system design ensures that the system was delivered, installed and commissioned with no hassles and all safety requirements to CAT 3 are met satisfactorily.

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Oats Handling System

As part of their expansion plant, a muesli manufacturer contacted Fresco Systems to assist in handling various types of oats to and from bulk bags.

Their processes require batching from bulk bags as raw materials and then filling bulk bags as finished products.

Being a new user to bulk bags, they were concerned with handling oats in bulk bags, in particular breakages and flowability. Fresco Systems recommended the electric hoist type bulk bag unloaders fitted with vibratory trays and metering screw feeders. The electric hoist enables the operator to handle bulk bags from pallet trucks in the process room rather than forklift. Once lifted, the bulk bags then rest securely on the vibratory tray.

The vibratory tray provides acts as a gentle flow aid compared to the paddles of the bag massagers which might damage the products. The spout clamp then seals the bulk bag spouts creating dust tight, secure attachment, totally enclosing the interface between the bulk bags and the feeder hopper below.

To eliminate the risk of breakage, a larger feeder screw was selected with minimal clearance between the screw edge and the outer tube. This eliminates the risk of the product pinching and breaking during feeding. The bulk bag unloaders are on loadcells which enable the operators to key in desired amounts of product to be batched out.

The end result is an effective way of handling and batching fragile products from bulk bags.

At the end of the process, two bulk bag fillers are positioned side by side to allow continuous feeling of bulk bags. The bi directional belt conveyor feeds into a bulk bag while the other filled bulk bag is being replaced. Once the operator connected an empty bulk bag to the fill head and press the ready button, the bag inflators remove creases and folds in the bags which can cause irregular filling of the bag, making it unstable. The bulk bag fillers are also on loadcells and the belt conveyor feeds each station until the desired weight is reached.

Stand alone control systems were supplied with all systems with the capabilities of communicating to the plant PLC.

As Fresco Systems consulted with the client from concept stage, delivery and commissioning of the systems have been seamless and the customer is now discussing further system upgrades increase their capacity.

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Cone Blender

Fresco Systems recently completed a project for a 50litre laboratory sized cone blender for mixing specialist anti metallic reference materials.

The customer had specific requirements they were unable to source until Fresco offered a bespoke solution based on their standard cone blender design.

The specification included homogeneous blending, no metallic contact surfaces, easy clean design, manual loading and unloading. To achieve this Fresco designed and manufactured a cone blender with split body, used a baked on Teflon coating for the contact surfaces and a plastic discharge valve.

The high reduction direct drive geared motor allowed for positioning of the blender in the load and unload positions without the use of an ancillary brake.

The standard range of Fresco cone blenders includes blending capacities from 50litres to 2,000litres, includes braked motors, access hatches for loading and cleaning as well as various discharge valves and accessories. Materials of construction to suit the application with polishing to pharmaceutical standards or as required. Safety guarding including fixed or light curtain to cat3 standards.

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Inflatable 25 kg Bags Fill Head

A recent enquiry was a request by an existing customer to use one of our bulk bag clamping fill heads in an application to fill 25kg bags.

Although a good idea, there were a few challenges in using the same fill head for 25kg bagging.

Their current process involved bagging off directly from a blender in an elevated position with control being through a continuously variable butterfly valve operated by foot control. The 25kg bag they were filling was simply wrapped around the discharge chute and held by the operator on a manual weigh platform. The operator watched the weigh display and at the right time closed the butterfly valve. Sounds familiar?

This was a cost effective, and quick process however dusty due to lack of control of dust laden displaced air, inaccurate and inconsistent due to the operator reacting to the weigh controller readout, and finally, not best practice from an OH&S perspective as the bag had to then be lifted onto the conveyor mounted under the sealing head which was a further separate disjointed process.

Capital was constrained so moving to an automated bagging system was prohibitive.

After a site visit to get good clarity on what the customer was really trying to achieve, and working with the customer, we were able to modify and tailor an inflatable Fresco fill head to fit up to an old unused semi automated weigh bag filling machine that the customer had unused. Factory acceptance test then proved the ability to control the inflatable fill head pressure just enough so the bag could hold the drop of 25kgs of product, but not too much so that it split the empty bag each time.

The result was a dust free bagging process that maintained the speed of the original manual process and delivered consistent accurate bag fill weights. A subtle drop by the full bag when released by the inflatable fill head put the full bag directly onto a slide plate from which the operator could slide the bag directly onto the conveyor under the seal head, thereby reducing the OH&S issues in the process.

Contact us for your complete bulk materials handling solution.

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Pneumatic Hopper Discharge Flow Aid Devices

Pneumatic Hopper Discharge Flow Aid Devices

Vessels of many shapes and sizes have since been built through a process of trial and error, to store a huge range of bulk materials in virtually all spheres of industry. Particle technology has evolved considerably over the last 50 years, to produce a coherent set of theories and design guidelines.

However, there are many challenging materials whose behaviour cannot be easily accommodated hopper design i.e., fibrous, spring-like, wet / moist, stick & tacky, visco-elastic, highly compressible, caking prone and very fine bulk materials. For these types of materials, applications where conventional design does not provide an acceptable solution and retrofit situations where operating difficulties are encountered, discharge aids or discharge systems are often used to secure discharge and empty the contents of silos.

These devices are almost invariably selected based on past industrial experience or by a process of trial & error. Selection must take into account constraints that are imposed by the process and the available space. There is usually a significant economic penalty for incorrect or sub-optimal choice of a discharge system in terms of extended commissioning costs, production delays and interruptions, loss of output, product wastage, loss of quality, increased maintenance and manual attention cost.

Due to the many industries these flow problems are found, and their specific requirements, a Fresco Systems engineer will visit site to discuss your particular requirements in detail. If the facility into which a system is being considered exists the engineer will carry out a detailed survey, if a new facility we would work from project drawings. We have 20 plus years of combined experience in the design of discharge aids or discharge systems, with installations across a whole spectrum of industries from pharmaceutical and production facilities to mineral processing and power generation.

The objective of this paper is to summarise information on pneumatic air flow aid discharger device that are currently prevalent in industry. An effort is also made to provide guidelines for their selection and specification as part of an integral design, or for retrofit to overcome operating problems.


Discharge aids may be defined as devices that stimulate or improve bulk solids flow out of bulk storage container. Items may be installed downstream of discharge aids to provide a means to shut off or regulate the flow of bulk solids. Slide gate valves and feeders are examples of discharge controllers. A discharge system can either be integrated with the silo or installed as an add-on, depending on the design and reason for its inclusion.

It is important to distinguish between the basic objectives of discharger aids and those of feeders to avoid misapplications. The primary purpose of a discharger aid is to promote flow, not necessarily to regulate it, and without regard to the order of zone discharge. A feeder, on the other hand, depends on the material flowing reliably to its inlet. Feeders influence the flow regime developed in the storage container and will not function if flow in the bin is unreliable. A feeder and its supply hopper are therefore an integral system.

Types of Flow Problems

The more common forms of flow difficulty are concerned with the restriction of flow, either complete or erratic stoppages, or a delivery rate less than that required. Circumstances also arise where the discharge rate is in excess of requirements, uncontrollable, in an unsuitable condition for handling, process or use or is incomplete. These difficulties arise for a number of different reasons, such as:

  • Arching: where the product forms a blockage over the outlet and flow ceases. Two basic types of arch can create a stable obstruction over a hopper outlet. One is that created by the bulk strength of a cohesive material being able to span the dimension of the opening. The other is when lumps come together to make a continuous structural across the orifice by virtue of the contact points offering a static relationship that makes a continuous load path as in a bridge.
  • Rat Holing (Piping): where material empties from a central core above the outlet up to the surface level of the stored material but no further product collapses into the empty flow channel.
  • Irregular flow: where the discharge rate is erratic or subject to cyclic variations, that is not compatible with the specific process requirements of the operation.
  • Flushing: a form of uncontrollable flow, generally due to the presence of excess air or gas in the voids that dilates the bulk material to a weak condition with virtually zero shear strength.
  •  Static zones: where subsequently problems occur due to deterioration of flow property or product quality because of extended residence time or Residue material unable to discharge by gravity.
  • Segregation: that leads to flow or processing difficulties or loss of quality.

All discharge aids work using one or more of the following principles:

  1. Dilate the material to enhance flow. The flow function of dilated material exhibits significantly lower unconfined yield strength (see Figure 3) thereby making it flow better. (Air injection may be used to dilate the bulk or inhibit time consolidation due to settlement).
  2. Induce stresses that exceed the strength of the bulk material. (Vibration and mechanical agitators may be used to deform the bulk).
  3. Reduce the friction between particles and the wall of flow channel. (Change the surface finish to a contact friction of lower value)
  4. Modify the flow regime to one more favourable to flow.
  5. Alter the bulk material flow properties by additives or surface modifiers. (Inhibit particle to particle adhesion or ‘caking’).

Pneumatic Discharge Aids

A wide range of pneumatic discharge aids are available in the market, namely

  • Aeration or fluidising pads, fluidising hoppers
  • Directed air-jet type (continuous and pulsed)
  • Pneumatically inflated dischargers or air pillows
  • Air cannons

Aeration or fluidising pads and fluidising hoppers

These discharge aid rely on dilation of bulk material (increase in inter-particle separation) by injecting air in the interstitial space between the particles. Powders tend to behave like fluids when fully aerated, but total fluidisation is not essential to promote the flow of fine particulate material, in fact doing so can result in the powder being difficult to control or not be in a suitable state for packing. Bulk materials comprised of particles of size less than 75 microns (-200 mesh), or with at least a 25% fraction less than 75 microns, (-200 mesh), are suitable candidates for aeration. However, powders with particles mostly less than 10 microns are very slow to settle, but difficult to re-fluidise, since they then exhibit channelling behaviour. Good air dispersion may be re-achieved by pulsing large airflow rates that creates shock waves to cause massive agitation.

There are two main techniques of employing product aeration:

  1. Air injection during discharge – This works by reducing the materials bulk strength and particle wall friction, particularly near the outlet region.
  2. Continuous air slide injection during storage – This works by inhibiting de-aeration and the gain of bulk strength of the whole mass due to time settlement.

It should be determined whether the bulk material has a tendency to flush/flood or flow uncontrollably in fluidised state. In such cases, option #2 is more suitable. The amount of air required to avoid high strength gain of fine powders due to time settlement is very small, but the technique is not appropriate for products that rapidly de-aerate (particle size greater than 200 microns).

Excessive fluidisation can result in bubbling and the elutriation of fines. It can also aggravate the segregation of coarse and fine fractions within the hopper.

Aeration or fluidisation pads are easily mounted on existing hoppers as retrofits, multi-layer metal mesh or woven media is typically used as air distributor. Uniform air distribution is achieved by maintaining a large pressure drop across the media. The air consumption is typically 8.5 m3/min per square metre of pad area. These inject air only when discharge is required. They generate a pressure differential between the injection points and the hopper outlet, providing both a driving force and a supply of air to satisfy the void demand of bulk expansion for flow.

Bulk control can be achieved by use of an aeration pad that covers the whole container base. Dilatation of the bulk improves the materials ‘flowability’ by reducing both wall friction and inter-particle cohesion. Activation of the entire hopper section allows a shallow hopper design to be employed. This may be supplied with a low, controlled-volume injection during storage, to stabilise the flow condition whilst the material is static, and increase the degree of aeration by injecting a higher rate of air for discharge. It is critical to supply oil free, clean and dry air for aeration to avoid product contamination. Appropriate arrangements must also be made to exhaust excess air and contain entrained dust at the top of the bin/silo.

case017_aDirected air jets

Directed jets can be effective in using the kinetic energy of air-jets to dislodge material from surrounding hopper wall and provide better gas dispersion through turbulence generation (Figure 1). The effective radius of these jets is limited to 1- 2 feet. Therefore, the jets must be placed in effective locations or multiple units need to be installed on the hopper wall to avoid dead zones. These jets can be timed and pulsed to minimise gas consumption. It is critical to supply oil free, clean and dry air to avoid contamination and prevent plugging of fine nozzles. The crucial flow region for discharge is that near the outlet, because the smaller span at this location is the most likely place for stoppages to form. Clearing this region, or part of the periphery of the orifice, is equivalent to having a larger opening that can be sufficient for the remaining contents to discharge.

Pneumatically Inflated Dischargers or Air Pillows

These are flexible bladders mounted on the cone or inclined walls of the bin/silo. Upon pressurisation (typically 1 to 3 bars), the flexible bladders expand and force the material towards the centre. They are helpful in breaking ratholes or “brittle arching”. These devices should not be used when the hopper outlet is closed or where the material is unable to flow, as local compaction will aggravate the flow difficulties, or with sharp or abrasive products that can puncture or wear through the flexible diaphragm.

case017_bAir Cannons

Air cannons (or blasters) are designed to inject blasts of high pressure gas, (up to 10 bars), in a short duration (typically fractions of a second). The shockwave traveling through the bulk solid provides a substantial force to break an arch or a rathole. Air cannons must be located where the stored material can be moved into an empty flow channel. Typical application includes use with sticky, wet, adhesive, fine, caking and fibrous materials. These devices are also used to knock sticky or adhesive materials and residual pockets of material from the walls of a bin/silo. The force created by discharging air cannons is directly proportional to the reservoir pressure. The duration of the pressure pulse depends on both the size of the reservoir and the initial air pressure. The blast from air cannons or blasters can be directed either tangentially, (along the wall), or into the bulk material at various angles. Various shapes of nozzles are available to create different dispersion patterns. When operating multiple air cannons, those at the bottom should be fired first, and the other moving progressively upwards at regular intervals. These devices should not be used for continuous operation. They are most useful for restarting flow after long downtime, after a process upset or for terminally clearing the bin after gravity flow has cleared what will discharge of its own accord. Every blast causes a reactionary force on the silo wall, so reinforcement of walls near the blasters fittings must be considered, especially for retrofit situations. Large chunks of caked or consolidated material may be dislodged from a wall, arch or rathole, to generate significant impact stresses within the silo. The silo and any associated equipment must accommodate such conditions.

Fresco Systems engineers are no strangers to devising ingenious and innovative solutions to assist you in creating a healthier and safer working environment.

Fresco Systems flexible approach means that whatever the application, no industry or production facility is precluded from a system installation.

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Robotic De-Palletising

Fresco has just supplied and installed a two line robotic de-palletising system for one of the worlds largest dairy companies.

Fresco has just supplied and installed a two line robotic de-palletising system for one of the worlds largest dairy companies.

Designed to eliminate manual handling, improve hygiene standards and reduce labor costs. The most challenging aspects of the project was the strict hygiene and safety criteria’s and the system also had to fit within the existing building envelope.

Full size double pallets are loaded through a rapid roller door by forklift and wait for the scissor lifter to be raised before indexing into the unloading position. The conveyor system is controlled by a PLC with pallet positioning monitored by sensors and interlocked with a light curtain for safety. Pallet status is provided to the operators within the hygiene area and the forklift operators in the warehouse via visual light indication.

The robot then de-palletisers the 25kg bags automatically using a vacuum suction head to lift the bag and place it on a conveyor. Pallet / bag configuration is all programmable to suit the type of product and the configuration of the pallet stacking. If a bag is out of position the robot hunts for it within a defined area until the bag is found or it raises an alarm for the operator to assist. Bags removed by quality control are treated in the same manner. De-palletising rates are adjustable up to 600bags/hr per line.

Bags exit the caged area on a belt conveyor which feed the bags to an outer removal station where the operator removes the outer paper packaging before placing the plastic lined inner bags on another conveyor for transfer to the critical hygiene area. No manual lifting is required to remove the bag outers as the bag is flipped pneumatically. The waste packaging is removed and compacted for recycling.

The bags are discharged in to a bag dump station where the contents are dense phase vacuum conveyed to a receival hopper for further processing.

The system is designed to category 4 safety standards. This is achieved by the use of a 2.5m high physical barrier, light curtains, twin encapsulated key system on the access gate and a standalone safety barrier relay module prior to the PLC.